556 PHILOSOPHICAL TRANSACTIONS. [aNNO 1682-3 



Philips's calculation gave them, and therefore in the months of October and 

 November I began to observe them more diligently, and procured them to be 

 carefully noted by an ingenious friend at Tower-wharf. From these observa- 

 tions I raised a correction of Mr. Philips's numbers, and caused a tide-table to 

 be made agreeable to it, which was printed by Mr. Hook in his Philosophical 

 Collections, ]SI° 4. 



But the weather then proving stormy and unseasonable, I dare not rely on 

 those observations, nor that correction; therefore in the spring and summer 

 months following, of the year 1 682, I began to observe them again, and with 

 the help of my friends and servants, I noted the times of above 80 high-waters 

 at Tower-wharf and Greenwich, by which I found that the greatest and least 

 differences between the moon's true southing and the high-waters were not, as 

 Mr. Philips had placed them, at the full or new and quarter moons, but the 

 greatest nearer to the neaps, the least to the highest spring-tides. I found also 

 that the inequality was not the same that he had made it ; and after a trial or 

 two, that I could represent and answer above 6o of these observations with less 

 than one quarter of an hour's difference; which, considering how difficult it is 

 to determine the time of a high-water exactly, I cannot but esteem a very 

 good agreement. 



Hitherto our tide- tables have only showed the time of that one high- water 

 which next follows the moon's southing; but in this new table T have given the 

 times of both, concerning which, I desire it may be noted, that when, by rea- 

 son of great droughts in summer, or extreme frosts in winter, the springs are 

 low, and the fresh waters less than usual, the tides may hold up longer than the 

 times noted in the table; as also when strong north-westerly or northerly 

 winds blow, which bring in an extraordinary flood from the northern seas, and 

 keep it up longer than other times. So on the contrary, when the winds blow 

 hard on the opposite points of the compass, or when we have much rain and 

 great freshes, the tides hold not out so long as the times showed in the table, 

 the freshes overpowering and checking them sooner; yet have I never found 

 that the differences between the calculated and observed high-waters have 

 much exceeded half an hour; most commonly they are scarcely half so 

 much. 



This table may be reduced and made to serve for any other port of his ma- 

 jesty's dominions and neighbouring countries, by only subtracting or adding so 

 much time to the high-waters noted in it, as the high-water observed in the 

 said place shall be found to precede or follow the time of the high-water the 

 same day. For by such accounts as I have met with and received of the tides 

 in remote places, I find there is every where, about England, the same dif- 



